This paper studies how the continuity and uniformity are achieved in the 16th century polyphony through the imitation technique and cadential formula. Usually imitation technique is needed for the beginning and cadence for closing in the polyphony texture but these two are overlapped in inner cadences thus producing meshed opening and ending in progressions. Cadence is a device for bringing a pause or a close in a section. In spite of that inner cadences should produce a double effect of termination and continuity before the final cadence in order to show coherence. In this sense intensity is important in inner cadences. Imitation is a tool for repetition. Imitation in perfect interval according to hexachord system confrims the fact that “a melody” is repeated by several voices in different register. Sharing a melody denotes uniformity while voices beginning in various time difference represent continuous flow of time. Imitation happens at the beginning of a phrase but it overlaps with the cadence of the previous phrase creating a continuity naturally between two phrases.

The 2nd piece, 「Selbstportrait」 mit Reich und Riley of Drei Stu¨cke fu¨r zwei Klaviere composed in 1976 is a typical example of minimal music among Gyo¨rgy Ligeti's works. In this opus, a musical citation(Zitat) is an important thing. It is not directly performed, i.e., it is an indirect citation about musical features and phenomena of minimal music, not a direct one about a certain composer's piece. However, we can find out obviously that Ligeti's ideas and musical phenomena which was accepted as a new element of his creation in 1970's already occupied an important position in his works before 1970's through a lot of his pieces of 1960's and 『Musica ricercata』 (1951-1953) composed in his time in Hungary. The similarities among his pieces composed before he came to know minimal music can be explained by the identity of his unconscious musical tendency which is 'floated in the air' like his own expression. As we can see in the title, 「Selbstportrait」 mit Reich und Riley, the way of citation in this piece is one that a citation of musical expression inherent in his own works is colored by something as that about phenomena of minimal music. The citation of this kind about ideas of minimal music was more emphasized by accommodation of various sorts of traditional music in this piece. 「Selbstportrait」 mit Reich und Riley received musical traditions such as cluster technique, blocked keyboard, imitation technique and inherence of F. Chopin's music. Such a musical accommodation make us unable to perceive citation and accommodation in its acoustic result due to citation of harmonics in the pieces of Henry Cowell and Pierre Boulez, techniques for organ by Karl-Erik Welin or blocked keyboard of Henning Skdentopf. The citation of blocked keyboard emphasized no more than that of minimal music by which he was influenced when he composed it. Therefore, we can regard the citation of minimal music in 「Selbstportrait」 as new musical phenomenon firmly expressed by the collage of Ligeti's mode, which is equal to minimal music, and other various musical mode of expression. In other words, various musical expressions collaged in 「Selbstportrait」 embodied the citation of minimal music as a unified phenomenon of constitution of the whole work, and the citation of minimal music in this piece came to have its own adequacy. The citation in Ligeti's works, especially that of his own pieces, is different from Zitat music or the mode of citation which aims at pursuing diversity as an important musical phenomenon coincided with Postmodernism in 1970's. One of the differences between them is that in Ligeti's works, the object of the citation is not a definite part of existing music but a entirely musical phenomenon. Another is that various musical expressions collaged are harmonized in the unity of the works.